Systems for Path Compensation with a Moving Objective

This application claims priority of U.S. application 63/410,700 which was filed on 28 Sep. 2022 and which is incorporated herein in its entirety by reference.

The description herein relates generally to optical systems utilized for measurement or metrology. More particularly, the disclosure includes apparatuses for compensating changes in a beam path in systems that have a moving objective.

A lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device (e.g., a mask) may contain or provide a pattern corresponding to an individual layer of the IC (“design layout”), and this pattern can be transferred onto a target portion (e.g., comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate contains a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatuses, the pattern on the entire patterning device is transferred onto one target portion in one go; such an apparatus may also be referred to as a stepper. In an alternative apparatus, a step-and-scan apparatus can cause a projection beam to scan over the patterning device in a given reference direction (the “scanning” direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively. Since, in general, the lithographic projection apparatus will have a reduction ratio M (e.g., 4), the speed F at which the substrate is moved will be 1/M times that at which the projection beam scans the patterning device. More information with regard to lithographic devices can be found in, for example, U.S. Pat. No. 6,046,792, incorporated herein by reference.

Prior to transferring the pattern from the patterning device to the substrate, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures (“post-exposure procedures”), such as a post-exposure bake (PEB), development, a hard bake and measurement/inspection of the transferred pattern. This array of procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, chemo-mechanical polishing, etc., all intended to finish off the individual layer of the device. If several layers are required in the device, then the whole procedure, or a variant thereof, is repeated for each layer. Eventually, a device will be present in each target portion on the substrate. These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc.

Thus, manufacturing devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, lithography, etch, chemical-mechanical polishing, and ion implantation. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. This device manufacturing process may be considered a patterning process. A patterning process involves a patterning step, such as optical and/or nanoimprint lithography using a patterning device in a lithographic apparatus, to transfer a pattern on the patterning device to a substrate and typically, but optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a bake tool, etching using the pattern using an etch apparatus, etc.

As noted, lithography is a central step in the manufacturing of device such as ICs, where patterns formed on substrates define functional elements of the devices, such as microprocessors, memory chips, etc. Similar lithographic techniques are also used in the formation of flat panel displays, micro-electro mechanical systems (MEMS) and other devices.

As semiconductor manufacturing processes continue to advance, the dimensions of functional elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend referred to as “Moore's law.” At the current state of technology, layers of devices are manufactured using lithographic projection apparatuses that project a design layout onto a substrate using illumination from a deep-ultraviolet illumination source, creating individual functional elements having dimensions well below 100 nm, i.e. less than half the wavelength of the radiation from the illumination source (e.g., a 193 nm illumination source).

This process in which features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed, is can be referred to as low-k1 lithography, according to the resolution formula CD=k1×λ/NA, where λ is the wavelength of radiation employed (e.g., 248 nm or 193 nm), NA is the numerical aperture of projection optics in the lithographic projection apparatus, CD is the “critical dimension”—generally the smallest feature size printed-and kl is an empirical resolution factor. In general, the smaller k1 the more difficult it becomes to reproduce a pattern on the substrate that resembles the shape and dimensions planned by a designer in order to achieve particular electrical functionality and performance. To overcome these difficulties, sophisticated fine-tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These include, for example, but not limited to, optimization of NA and optical coherence settings, customized illumination schemes, use of phase shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as “optical and process correction”) in the design layout, or other methods generally defined as “resolution enhancement techniques” (RET). The term “projection optics” as used herein should be broadly interpreted as encompassing various types of optical systems, including refractive optics, reflective optics, apertures and catadioptric optics, for example. The term “projection optics” may also include components operating according to any of these design types for directing, shaping or controlling the projection beam of radiation, collectively or singularly. The term “projection optics” may include any optical component in the lithographic projection apparatus, no matter where the optical component is located on an optical path of the lithographic projection apparatus. Projection optics may include optical components for shaping, adjusting and/or projecting radiation from the source before the radiation passes the patterning device, and/or optical components for shaping, adjusting and/or projecting the radiation after the radiation passes the patterning device. The projection optics generally exclude the source and the patterning device.

A system is disclosed that includes a mirror set comprising a first mirror, a second mirror, and a movable stage to which the mirror set is mounted to cause the first mirror and the second mirror to move together with the movable stage. The first mirror is configured to receive a beam at a first angle from an axis of the mirror set. The second mirror is configured to provide the beam at a second angle from the axis of the mirror set, the beam providing an output after reflection by the second mirror. Movement of the mirror set parallel to the axis results in a parallel shift of the output along the beam and movement of the mirror set perpendicular to the axis results in a perpendicular shift of the output perpendicular to the beam.

In some embodiments, the beam is a light beam from a light source in an optical scanning device and output can be a focus point of the light beam.

In some embodiments, the system can further include an objective to receive the output and configured to move with the movable stage where, during movement of the movable stage and objective, the output remains stationary with respect to the objective.

In some embodiments, an angular ratio that is a ratio between the first angle and the second angle determines a movement ratio of the movable stage that is an amount of movement at the output compared to an amount of movement at the movable stage. The angle between the input and the output can be 120 degrees thereby causing the ratio to be 1.

In some embodiments, the system can include an objective for receiving the output, the objective configured to move with the movable stage in a first direction. The system can also include a first static mirror configured to direct the beam to the objective where moving the movable stage and the objective along the first direction retains the position of the output at the objective along a second direction.

In some embodiments, the objective can be mechanically coupled to the movable stage or electronically controlled to move correspondingly to movement of the movable stage. Movement of the movable stage in the second direction can cause a corresponding movement of the output relative to objective.

In some embodiments, the system can further include an objective for receiving the output, the objective configured to move with the movable stage in a first direction and/or a second direction. A first static mirror can be configured to redirect the beam to the objective and a second static mirror can be configured to direct the beam to the first static mirror. Moving the movable stage and the objective to maintain a displacement along the first direction and along the second direction retains a position of the output at the objective.

In some embodiments, the system can further include a second static mirror configured to direct the beam to the mirror set and a second mirror set oriented perpendicular to and out of a plane of the mirror set and configured to direct the beam from the second mirror set to the mirror set. There can be a second movable stage to which the second mirror set is mounted and a third static mirror configured to direct the beam from the second mirror set to the second static mirror, where moving the second mirror set in the first direction allows adjustment of the output in the first direction, moving the second mirror set in the second direction allows adjustment of the output in the second direction, and moving the second mirror set in the third direction does not change a location of the output in the third direction.

In some embodiments, the system is configured for the second mirror set and the objective to move in the second direction relative to the mirror set, thereby causing the output to move along the second direction.

In some embodiments, the objective is further configured to move in the second direction independently of the mirror set, wherein maintaining a displacement between the second mirror set and the objective in the second direction retains the position of the output relative to the objective in the second direction.

In some embodiments, the system further includes an objective for receiving the output, the objective configured to move with the movable stage to maintain a same displacement between the objective and the movable stage in both a first direction and a third direction. The system can also include a first static mirror configured to direct the beam to the objective, a second static mirror configured to direct the beam to the first static mirror, and a folding mirror coupled to the movable stage and configured to turn the beam to be along a second direction, where moving the movable stage and the objective to maintain the displacement retains a position of the output at the objective along the second direction.

Metrology system (e.g., electron beam, optical, etc.) can be utilized to measure and/or characterize printed products (e.g., semiconductor chip wafers) or other manufactured components. For example, during or after the manufacture of a wafer for semiconductor processors, memory, etc., the features printed or etched on the wafer can be measured to determine how well the product matches a target pattern. These measurements can include measuring aspects such as critical dimensions (CDs), overlay, edge placement error (EPE), etc. The present disclosure primarily relates to measurements with optical metrology systems that provide light to the surface of the target product and then detect and analyze the light to generate an image of the target for further analysis.

is a diagram of a dual objective metrology system having a moving objective, according to an embodiment of the present disclosure. Some metrology systems can allow parallel measurements of multiple targets (e.g., wafers) through two separate objectives. As shown in, a metrology systemcan include a source/sensorwhose illumination light is split between two objectives,. This architecture can have at least one of the objectives able to move, for example to enable the ability to measure targetsseparated by varying distance, for example either due to being separate targets, or due to misalignments between two wafers that are being measured simultaneously. The split light can be directed through two mirror sets,, with at least portions of one mirror set (e.g., mirror set) able to move with objective.

is a diagram of a metrology system with a mirror set for directing light to/from an objective, according to an embodiment of the present disclosure.includes numerous features described with regard to(e.g., objective, target, source/sensor). As also shown by the simplified example in, the present disclosure provides numerous embodiments that permit a light beamfrom a source/sensorto be delivered to an objective. In various embodiments, this can be accomplished by having the objectivemove relative to some components of the system but be stationary relative to at least some portions of a movable stagethat can hold a mirror set. For example, the objectivecan be fixed to the movable stageso they move together or, in other embodiments, objectivecan be independently controlled to move in synch with some portions of the mirror set.

is a diagram of a mirror set that compensates for movement of a movable stage, according to an embodiment of the present disclosure.depicts a system, which, because of the geometry of the example mirrorsin mirror set, can be insensitive to (also referred to herein as “compensating for”) movement of the movable stage in certain directions. Such a system can enable a shifted light beam(e.g., shifted relative to a movable stage) to reach a target and/or light from a target to return along the same path to a sensor. In some embodiments, the beam can be a light beam from a light source in an optical scanning device or metrology system such as those depicted in. The system depicted inincludes a mirror sethaving a first mirror(taken here to receive a light beamillustrated by the dashed line) and a second mirror(shown here as providing the beamafter reflecting off first mirrorand second mirror). There can be a movable stageto which the mirror setcan be mounted to cause the first mirrorand the second mirrorto move together with the movable stage. A movable stage can be, for example, an optical table, a plate, or any other object to which the mirrors/optics can be mounted and can be configured to move in one or more directions, such as with motors, on tracks or rails, with belts, with piezoelectric transducers, etc. As shown, first mirrorcan be configured to receive beamat first anglefrom an axisof the mirror set. First anglecan be any angle between 0 and 180, for example, +75, 60, 45, 30, 15 or degrees. Similarly, second mirrorcan be configured to provide beamat a second anglefrom the axisof the mirror set, with the beamproviding an output(e.g., a focus point of a light beam, a light spot, etc.) after reflection by the second mirror. Outputcan be at any point along the beam path after the final mirror in the mirror set.

In general, movement (e.g., parallel movement) of the mirror setparallel to axiscan result in a parallel shiftof the outputalong the beam (i.e., parallel to the beam direction at the target). For example, as shown, movement in the Y direction (along axis) acts to shorten/lengthen the beam path without changing any angles of reflection. In the example where the output is a focus point of the light beam, this has the effect of moving the focus point but without moving the focus point perpendicular to the beam path. Similarly, movementof the mirror setperpendicular to axiscan result in a perpendicular shiftof the outputperpendicular to the beam. An angular ratio (which can be the ratio between the first angleand the second angle) can determine a movement ratio of the movable stage. The movement ratio is the amount of movement at the output compared to the amount of movement of the movable stage. Specifically, in embodiments where first angleand second angleare the same, the ratio can change from 1.73 when the angles are both 30 degrees, to 1.0 when 60 degrees, to 0.52 when 75 degrees, etc. For example, if both angles are 60 degrees, then 1 mm of parallel movementcauses 1 mm of parallel shiftof output. While in some embodiments a ratio other than.may be useful, in most embodiments the angle between the input and the output (i.e., the sum of first angleand second angle) isdegrees thereby causing the ratio to be.. In embodiments where the angles are different, this can cause a compound motion where, e.g., in response to parallel movement, outputcan exhibit a parallel shiftbut also a perpendicular shift.

Though not shown in, in any of the embodiments herein, the system can include an objective to receive the output and configured to move with the movable stage. As also shown in numerous embodiments herein, during movement of the movable stage and objective, the output can remain stationary with respect to the objective. As described previously, any of the objectives herein can be configured to move with the movable stage by being mechanically coupled to the movable stage or can be independently (e.g., electronically) controlled to move correspondingly to movement of the movable stage. As used herein, “mechanically coupled” or just “coupled” means that there is a rigid connection (e.g., the objective is somehow fastened to the movable stage). While the objective can be a lens that focuses on a wafer or other target, the objective can be any other optical component such as, lenses, mirrors, etc. or any component that may need the beam at a certain focal position. Also, though the objective is recited as included in many embodiments, the present disclosure contemplates that the objective is not required to be included in any embodiment's particular physical system. For example, some embodiments can include only the mirror system, with the objective, movable stages, etc. supplied separately for use as described herein.

A number of embodiments herein are described with reference to an orthogonal X-Y-Z coordinate system. This is for explanatory purposes only and as such no embodiment requires any particular orientation. The X-direction is referred to herein as a “first direction” (and can be positive or negative) and the Z-direction is referred to herein as a “second direction” (and can be positive or negative). Some embodiments can include a Y-direction that is referred to herein as a “third direction” (and can be positive or negative).

is a diagram of a mirror set that compensates for movement of a movable stage and

delivers a beam to an objective, according to an embodiment of the present disclosure. This mirror set is depicted as being in an X-Z plane.is also similar towith many of the elements reproduced therefrom. However, the embodiment depicted inalso includes an objectivefor receiving output. The objectivecan be configured to move with the movable stagein a first direction, for example by mechanical coupling or by being electronically controlled to move correspondingly to movement of the movable stage. Some embodiments can include a first static mirrorconfigured to direct the beamto the objective. As used herein, the term “static” means “stationary relative to the input light beam” (e.g., stationary relative to the light source, the last optical component before the beam reaches the mirror set, etc.). While a static mirror may be capable of movement in some embodiments, as used herein any static mirrors are considered to remain in place with respect to any movements of the movable stages.

With the first static mirroressentially redirecting the outputto objective, moving the movable stage and the objectivealong the first direction (e.g., the X direction) retains the position of the outputat the objectivealong a second direction (e.g., the Z direction). Similarly, in some embodiments, movement of the movable stagein the second direction can cause a corresponding movement of the outputrelative to objective.

are diagrams of alternative configurations of mirror sets, according to various embodiments of the present disclosure. These alternative configurations perform similar functions as the embodiment of. However, as can be seen, the various mirrors and movable stages in the mirror sets have different geometries. Element numbers are reproduced from corresponding elements of, but withdesignations (A, B, or C) appended (e.g., movable stageA inis similar to movable stagein).

is a diagram of a mirror set that allows for movement with two degrees of freedom, according to an embodiment of the present disclosure. This embodiment is similar to that of, but in particular with mirror setinverted and the addition of static mirrors,and objective. Objectivecan receive the output, with the objectiveconfigured to move with the movable stagein a first direction (e.g., X direction) and/or a second direction (e.g., Z direction). The system can also include a first static mirrorconfigured to redirect the beamto the objectiveand a second static mirrorconfigured to direct the beamto the first static mirror.

The system can be configured such that moving the movable stageand the objectiveto maintain a displacement along the first direction and along the second direction retains the position of the outputat the objective. As used herein, the phrase “maintaining a displacement” means that certain elements of the system (e.g., movable stageand objective) move together, e.g., via mechanical coupling or independent but synchronized control. This also means that the movable stageand objectiveare free to move in the X-Z plane as shown with the outputremaining at the same place in the objective.

is a diagram of multiple mirror sets that allow for movement perpendicular to the plane of one of the mirror sets, according to an embodiment of the present disclosure.includes diagramdepicting a three-dimensional view of an embodiment having multiple mirror sets disposed in orthogonal planes. Also shown are diagramillustrating components in the Y-Z plane and diagramillustrating components in the X-Z plane. The depicted system builds on the embodiment of(having a mirror set in an X-Z plane) by including another mirror set in an orthogonal plane (e.g., the Y-Z plane) that is therefore configured to allow movement of the objective in the Y direction.can also be understood by folding diagramto bedegrees “out of the page” similar to that depicted in diagram. Also, the beamleaving diagramis the input beam in diagram.

In addition to the elements depicted in(some of which are reproduced in diagrams,, and) some embodiments can include a second static mirrorconfigured to direct the beamto the mirror set(in diagram). Also shown is a second mirror set(in diagram) oriented perpendicular to, and out of the plane of, mirror setand configured to direct the beamfrom the second mirror setto mirror set. A second movable stageis shown to which the second mirror setcan be mounted. Second movable stageand second mirror setcan be similar to the movable stage and mirror set of, but in this embodiment second mirror setis inverted. There can also be a third static mirrorconfigured to direct the beamfrom the second mirror setto the second static mirror. The embodiment ofis therefore configured such that moving the second mirror setin the second direction allows adjustment of the outputin the second direction, moving the second mirror setin the third direction allows adjustment of the outputin the third direction, and moving the second mirrorset in the first direction does not change a location of the outputin the first direction. Similarly, moving the first mirror setset in the first direction allows adjustment of the outputin the first direction, moving the first mirror setin the second direction allows adjustment of the outputin the second direction, and moving the first mirror setin the third direction does not change a location of the outputin the third direction.

In some embodiments, the system can be configured for the second mirror setand the objectiveto move in the second direction relative to the mirror set, thereby causing the outputto move along the second direction. In other embodiments, mirror setand objectivecan move in the second direction relative to the second mirror set, thereby also causing the outputto move along the second direction.

In some embodiments, objectivecan be further configured to move in the second direction independently of the mirror set. In such embodiments, maintaining a displacement between the second mirror setand the objectivein the second direction retains the position of the outputrelative to the objectivein the second direction.

is a diagram of a mirror set that includes a turning mirror for the objective, according to an embodiment of the present disclosure. The embodiment ofdepicts a mirror set that can have the objective oriented perpendicular to the plane of the mirror set. For example, mirror setcan be mounted horizontally (e.g., in the X-Y plane) with the objectiveoriented vertically (e.g., along Z).also builds on the embodiment ofbut can further include an objective(similar to that in) for receiving the output. The objectivecan be configured to move with the movable stageto maintain a same displacement between the objectiveand the movable stagein both a first direction (e.g., in X) and a third direction (e.g., along Y). The system can also include a first static mirrorconfigured to direct the beamto the objectiveand a second static mirrorconfigured to direct the beamto the first static mirror.

The system can also include a folding mirrorcoupled to the movable stageand configured to turn the beamto be along a second direction (e.g., along Z). The folding mirror can be any type of mirror but is described herein as “folding” in that the folding mirror “folds” the beam from being in the X-Y plane, as shown, to going along Z (or any other direction in other embodiments). Accordingly, in such embodiments, moving the movable stageand the objectiveto maintain the displacement can retain the position of the outputat the objectivealong the second direction (e.g., along Z).

As previously mentioned, the embodiments disclosed herein can improve measurements and/or metrology of devices manufactured such as with lithographic processes. Examples of lithographic systems that the disclosed embodiments can be used with are described below.

is a block diagram of an example computer system CS, according to an embodiment of the present disclosure.

Computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processor) coupled with bus BS for processing information. Computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to bus BS for storing information and instructions to be executed by processor PRO. Main memory MM also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor PRO. Computer system CS further includes a read only memory (ROM) ROM or other static storage device coupled to bus BS for storing static information and instructions for processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to bus BS for storing information and instructions.

Computer system CS may be coupled via bus BS to a display DS, such as a cathode ray tube (CRT) or flat panel or touch panel display for displaying information to a computer user. An input device ID, including alphanumeric and other keys, is coupled to bus BS for communicating information and command selections to processor PRO. Another type of user input device is cursor control CC, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor PRO and for controlling cursor movement on display DS. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

According to one embodiment, portions of one or more methods described herein may be performed by computer system CS in response to processor PRO executing one or more sequences of one or more instructions contained in main memory MM. Such instructions may be read into main memory MM from another computer-readable medium, such as storage device SD. Execution of the sequences of instructions contained in main memory MM causes processor PRO to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory MM. In an alternative embodiment, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, the description herein is not limited to any specific combination of hardware circuitry and software.

The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor PRO for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-transitory, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge. Non-transitory computer readable media can have instructions recorded thereon. The instructions, when executed by a computer, can implement any of the features described herein. Transitory computer-readable media can include a carrier wave or other propagating electromagnetic signal.

Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor PRO for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system CS can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus BS can receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO retrieves and executes the instructions. The instructions received by main memory MM may optionally be stored on storage device SD either before or after execution by processor PRO.

Computer system CS may also include a communication interface CI coupled to bus BS. Communication interface CI provides a two-way data communication coupling to a network link NDL that is connected to a local network LAN. For example, communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interface CI may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface CI sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

Network link NDL typically provides data communication through one or more networks to other data devices. For example, network link NDL may provide a connection through local network LAN to a host computer HC. This can include data communication services provided through the worldwide packet data communication network, now commonly referred to as the “Internet” INT. Local network LAN (Internet) both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network data link NDL and through communication interface CI, which carry the digital data to and from computer system CS, are exemplary forms of carrier waves transporting the information.

Computer system CS can send messages and receive data, including program code, through the network(s), network data link NDL, and communication interface CI. In the Internet example, host computer HC might transmit a requested code for an application program through Internet INT, network data link NDL, local network LAN and communication interface CI. One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor PRO as it is received, and/or stored in storage device SD, or other non-volatile storage for later execution. In this manner, computer system CS may obtain application code in the form of a carrier wave.

is a schematic diagram of a lithographic projection apparatus, according to an embodiment of the present disclosure.

The lithographic projection apparatus can include an illumination system IL, a first object table MT, a second object table WT, and a projection system PS.